The first wave of Bush’s surge—3,200 troops—has arrived in Baghdad only to experience the most violent day for U.S. forces in two years. 25 American soldiers died on Saturday.

BBC:

As the deployment began, the US military said four soldiers and one marine had been killed in the restive western province of Anbar.

It took to 25 the number of US deaths in Iraq on Saturday - one of the worst days for US troops since the invasion.

[...]Saturday was the deadliest day for US troops in Iraq since January 2005, when 36 service members were killed. In addition to the deaths in Anbar:

Twelve US troops were killed in a helicopter crash near Baghdad Five US soldiers were killed in a clash with militants in the Shia holy city of Karbala Three other soldiers were killed in separate attacks across the country